Dimethyl sulfoxide (DMSO) [MAK Value Documentation, 2016]

Abstract

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the work place (MAK value) of dimethyl sulfoxide [ 67‐68‐5 ] of 50 ml/m 3 , considering the endpoints local and systemic toxicity as well as developmental toxicity. In a 13‐week inhalation study the olfactory and respiratory epithelia and the pharynx of rats are the target tissues, and a reduction of body weight gain, possibly secondary to the irritation, is seen. The NOAEC for these effects is 964 mg/m 3 (297 ml/m 3 , vapour). Since 2014 the Commission uses an empirical approach to set MAK‐values for substances with critical effects on the upper respiratory tract or the eyes. According to this approach, a MAK value of 50 ml/m 3 can be calculated from this study, taking into account that a lower NOAEC has to be expected with chronic exposure. Therefore, the previous MAK value is confirmed. As local effects are critical, the assignment to Peak Limitation Category I and the excursion factor of 2 are confirmed. In a screening study with rats according to OECD test guideline 421, the borderline increase in incidences of pups with dilated renal pelvis seen in a developmental toxicity study, are not confirmed. However, in rabbits, dimethyl sulfoxide causes kidney malformations with a NOAEL of 300 mg/kg body weight. Therefore, damage to the embryo or foetus cannot be excluded even when the MAK value is observed and dimethyl sulfoxide is assigned to Pregnancy Risk Group B.